1. Field of the Invention
The present invention relates to a magnetic head in which a conductor coil of the magnetic head is provided as a thin film conductor coil assembly, thereby to improve recording and reproducing characteristics of the magnetic head and also to facilitate miniaturization, and to offset external noises.
2. Description of the Related Art
In a conventional magnetic head, a magnetic head 3 is provided on a slider 2 forming rails 1 as shown in FIG. 20 thru FIG. 22. This magnetic head 3 consists of an I-core 4 and a U-shaped core 5, and an insulated coil 6 is wound around either the I-core 4 or the U-shaped core 5 (I-core 4 in FIG. 21). Further, a very small gap 7 is provided between the I-core 4 and the U-shaped core 5 so that a magnetic path 8 is formed between the I-core 4 and the U-shaped core 5. Inclined faces 9 on the air outflow side and inclined faces 10 on the air inflow side are formed on the rails 1 as shown in FIG. 20, so that the slider 2 is floated. Further, a wide space portion 11 is formed in the U-shaped core 5 so that the coil 6 may be wound around. In addition, the U-shaped core 5 such as shown in FIG. 25 is provided so as to project from an end surface of the slider 2 in a similar manner as in conventional examples shown in FIG. 23 and FIG. 24, and the coil 6 is wound around the U-shaped core 5. As to the other portions, the same symbols are assigned to those that are the same as FIG. 20 thru FIG. 22 and description thereof is omitted herein.
Magnetic recording has a tendency of densification at present. Therefore, the magnetic head has to be made small in size and light in weight in order to cope with such densification of the magnetic recording. However, the above-described conventional magnetic head has the following problems when the magnetic head is made small in size and light in weight.
Namely, the I-core and the U-shaped core also become small in size for miniaturizing a conventional magnetic head. Thus, since the space portion becomes too small to wind the coil around the small I-core or U-shaped core, a very fine coil has to be used. Thus, there have been such problems that the coil is broken in a coil winding process, insulation covering is peeled off, and inferior goods are generated, thus causing poor yield and low reliability. Further, it may be considered to wind the coil by hand as a countermeasure against the problems of yield and reliability, but there is a problem that the productivity is low. Because of such reasons, there has been a limit for making a magnetic head small in size and light in weight from a structural point of view in a magnetic head using a coil wound type conductor coil, thus making it impossible to sufficiently cope with densification of magnetic recording. Thus, a thin film magnetic head has been developed at present in order to solve these problems.
In the above-described thin film magnetic head, a magnetic head member 12 having a thin thickness of t has been provided at one end of the slider 2 as shown in FIG. 26. In this magnetic head member 12, gaps 7 are formed so as to form magnetic circuits 13 within the thin thickness of t as shown in FIG. 27.
The problems of a magnetic head using the above-described conventional coil winding type conductor coil are solved for the time being by means of the above-described thin film magnetic head member, but the following problems are encountered. Namely, since the magnetic circuits 13 are formed in the magnetic head member 12 having the thin thickness of t in the above-described conventional thin film magnetic head, the sectional area of the magnetic circuit becomes smaller and magnetic resistance is increased, thus causing a problem that induced electromotive force is reduced and recording and reproducing characteristics are lowered when the area of the magnetic circuit becomes smaller and the magnetic resistance is increased.
When this is explained theoretically, magnetic flux .PHI. of a magnetic core is proportional to a number of turns N and an electric current i of the coil, and is in reverse proportion to magnetic resistance Rm. When this relationship is formularized with an expression, .PHI.=Ni/Rm is obtained. Thus, it is required to make the magnetic circuit area larger and the magnetic resistance Rm smaller in order to increase the magnetic flux .PHI.. On the other hand, the induced electromotive force e required for reproduced output is proportional to the time differential of the magnetic flux .PHI.. When this is formularized with an expression, e=-N.times.d.PHI./dt is obtained. It is required to increase the magnetic flux .PHI. in order to increase the induced electromotive force e, and it is seen from the above expression that the magnetic resistance Rm has to be reduced by making the magnetic circuit area larger in order to increase the magnetic flux .PHI.. When the magnetic circuit area is small as described above, the magnetic resistance is increased and the induced electromotive force is reduced, thus lowering recording and reproducing characteristics.
Further, there are the following problems with the miniaturization of a magnetic head. That is, the induced electromotive force e has to be increased in order to improve reproduced output characteristics. In order to increase the induced electromotive force e, it is required to increase the magnetic flux .PHI. by enlarging the magnetic circuit area as it is apparent from the above-mentioned expression, and to reduce the time t for reading information out of one recorded portion on a magnetic disc. In order to reduce this time t, a linear velocity V of the magnetic head has to be accelerated. Namely, since the linear velocity V is a product of a distance L from the position of the magnetic head to the center of revolution of the magnetic disc by an angular rotational velocity .omega. of the magnetic disc, i.e., V=.omega.L, L has to be increased in order to accelerate the linear velocity V of the magnetic head. Since the diameter of the magnetic disc has to be made smaller by the demand for miniaturization of a magnetic disc drive, however, the fact is that the distance L from the position of the magnetic head to the center of revolution of the magnetic disc cannot be determined large in miniaturization. Accordingly, to facilitate miniaturizing the magnetic disc, increasing the induced electromotive force e and improving reproduced output, there is no choice but to increase the magnetic flux .PHI. by enlarging the magnetic circuit area, thus causing such a problem that a conventional thin film magnetic head having a small magnetic circuit area cannot sufficiently correspond to a miniaturized magnetic disc.
Balance winding of a coil is ideal for offsetting external noises, but, in a conventional thin film magnetic head, a magnetic circuit is formed in a thin film core so as to form a conductor coil and a core as one body into a thin film. Therefore, it is impossible to perform balance winding of a coil. As a result, there is such a problem that external noises cannot be offset.
It is an object of the present invention to provide a magnetic head in which, instead of forming both the conductor coil and the core as above-mentioned conventional thin film magnetic head, only the conductor coil is formed in a thin film, thereby to make the magnetic circuit area sufficiently large so as to reduce the magnetic resistance, to improve recording and reproducing characteristics, to facilitate miniaturization and also balance winding of a coil possible thereby to offset external noises, thus improving yield, reliability and productivity of a coil winding type magnetic head at the same time.